What is a surrogate key and when do you use one?

A surrogate key is a unique identifier for an entity in a database, typically an auto-generated number or alphanumeric value that has no intrinsic meaning. It is used instead of natural keys, which are derived from the data itself, to provide a stable and consistent way to identify records, especially when natural keys may change or are not unique. Surrogate keys are particularly useful in data warehousing and when dealing with large datasets, as they simplify relationships between tables and improve query performance. They also help maintain data integrity when integrating data from different sources.